A flash memory is one type of nonvolatile memory that is electrically programmable and erasable. As is known, the flash memory typically consists of an array of AND-type memory cells in which charging and discharging a floating gate, using a tunnel current, are performed for data writing and erasure.
As the present inventors examined such a flash memory, we have known that the flash memory is furnished with management information comprising power supply trimming data, bitline restoration data, and the like by programming fuses. When the flash memory is initialized upon its power-on or the like, the management information stored in the fuses of the flash memory are read, a fine adjustment of voltage that a power supply circuit generates is performed, and restoration of a defective memory cell or memory line is performed by replacing it with a spare row or column.
This type of semiconductor memory is described in detail in a journal “Denshizairyo” June issue, edited by Osima Msashi, Jun. 1, 1995, Vol. 34, No. 6, pp. 32–37, published by Kogyo Chosakai Publishing Co. Ltd, which is an example of prior art reference. In this reference, flash memory reading, writing, and easing operations and relations are described.
However, the present inventors found the following problems with the technique of programming the fuses of the flash memory to store the management information as mentioned above.
In programming the fuses to store the management information, a process of cutting the fuses must be performed, based on the result of inspection through a power supply trimming test and restoration test which are performed when a wafer is tested. This results in a problem of increasing the number of man-hours and a decrease in efficiency.
To cut the fuses, an apparatus for cutting the fuses by laser light such as laser repair is required. This results in a problem of an increase in flash memory production cost.
Once a fuse has been cut, it is impossible to connect it again. For example, in a flash memory development stage, the management information cannot be changed or modified flexibly, which results in a problem of a decrease in design development efficiency.
It is an object of the present invention to provide a nonvolatile semiconductor storage device whose initialization time is greatly reduced by reading management information at a higher speed and with accuracy and whose power consumption during operation can be reduced.
The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.